PERIPHERAL GLUCOSE-METABOLISM IN HEALTHY-SUBJECTS AND IN ENDOCRINE DISEASES

1. Seventeen healthy male subjects were studied after an overnight fas t (12-14 h) and for 3 h after ingestion of 75 g glucose to investigate peripheral glucose metabolism (uptake, oxidative and nonoxidative met abolism) using the forearm technique to estimate muscle exchange of su bstrate combined with indirect calorimetry. In normal subjects,during the 3-h study period, 30.3 +/- 2.1 g (40.4% of the ingested load) of g lucose were processed by skeletal muscle in the body as a whole and 8. 1 +/- 0.6 g were completely oxidized while 22.2 +/- 2.3 g were utilize d through the nonoxidative pathway in muscle tissue. 2. After ingestin g 75 g of glucose, normal women showed greater glucose uptake per unit of muscle mass and a predominant tendency toward utilizing glucose by a nonoxidative pathway than did normal men. The higher glucose uptake of the female group and an insulin response not significantly differe nt from that of the male group suggest that muscle insulin sensitivity is greater in normal women. 3. The study of the effects of 50 and 100 g glucose loads on the peripheral glucose metabolism of normal men re vealed a dose-dependent metabolic response in muscle tissue to these o ral glucose challenges with respect to forearm muscle glucose uptake a nd nonoxidative glucose metabolism. The oxidative responses of the mus cle tissue were not directly proportional to the oral glucose loads. 4 . The administration of carbohydrate, usually glucose, leads to a decr ease in the serum level of inorganic phosphorus (Pi), attributed to Pi flow from the extracellular to the intracellular compartment as part of the increased glucose metabolism induced by insulin. However, our d ata indicate that muscle tissue is not the site responsible for the fa ll in serum Pi after glucose ingestion.5. Spontaneous human hyperthyro idism increases glucose uptake by the forearm muscles in the postabsor ptive state and during an oral glucose challenge, with increased fluxe s of glucose through the oxidative and nonoxidative pathways.